Development of Large Wingspan Flapping-Wing Flying Robots With Improved Efficiency by Rigid-Flexible Coupling Flapping Mechanism

The flight efficiency of bionic flapping-wing robots is largely influenced by the flapping mechanism. This paper presents the development of a large wingspan flapping-wing flying robot that utilizes a rigid-flexible coupling flapping mechanism to reduce energy consumption, improve flight efficiency, and enhance wind resistance. The rigid-flexible coupling flapping mechanism consists of a DC motor with a gearset and a flexible flapping mechanism based on torsion spring. This mechanism combines the high torque driving capability of a rigid mechanism with the energy storage capacity of a flexible mechanism. Synchronizing the passive deformation of the torsion spring with the periodic acceleration and deceleration of the wings during the flapping cycle enables the storage, transfer, and release of kinetic energy and torsional spring elastic strain energy. Simulation studies show that the proposed design effectively reduces the peak power required. A prototype with a wingspan of 1.8 meters and a mass of 1.0 kilograms was developed. Compared to a rigid mechanism, the proposed design significantly reduces the electrical power consumption, especially when achieving flapping frequencies exceeding 1.5 Hz, as validated through wind tunnel experiments. At a flapping frequency of 2.2 Hz, the maximum reduction in electrical power consumption reaches 14.8%. The flexible elements also increased the downstroke ratio, consequently enhancing thrust and propulsion efficiency. Outdoor flight experiments have demonstrated that the prototype propelled by the rigid-flexible coupling drive mechanism consumes only 81.56 W during cruising, which is 8.78 W (9.72%) less than the rigidly driven prototype.